why is pi called pi

Pi is called “pi” because mathematicians in the early 1700s chose the Greek letter π as a neat shorthand for the circle’s perimeter (or “periphery”), and that stuck.

Quick Scoop

Where the name “pi” came from

• The number itself (the ratio of a circle’s circumference to its diameter) was known for thousands of years before it got the name “pi”.

• In 1706, Welsh mathematician William Jones was the first to use the Greek letter π specifically for this ratio in print.

• Swiss mathematician Leonhard Euler later adopted π in his hugely influential books, which helped make this notation standard worldwide.

Why the letter π?

• π is the Greek equivalent of “p”, and mathematicians linked it to words like “periphery” or “perimeter” of a circle.

• Before π caught on, people used long phrases such as “the quantity which, when the diameter is multiplied by it, yields the circumference” instead of a symbol.

• Using a single Greek letter was cleaner for formulas and teaching, which helped it become the preferred symbol.

A tiny timeline story

1. Ancient civilizations (Babylonians, Egyptians, Greeks) know the circle ratio and use rough approximations like 3 or 3.16, but no special symbol.

2. 1706 – William Jones prints π for the ratio of circumference to diameter.

3. 1730s and beyond – Euler uses π consistently; his textbooks spread throughout Europe, and π becomes the standard symbol we still use today.

In short: it’s called “pi” because early modern mathematicians picked the Greek letter that sounds like “p” for the circle’s perimeter, and Euler’s influence made that choice permanent.

TL;DR:
Pi got its name in 1706 when William Jones used the Greek letter π (for “periphery/perimeter”), and it became universal after Leonhard Euler popularized it.

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